If I uncheck and recheck "Enable Networking" in the Network Manager Applet 0.7.996 I would expect the wired network to disconnect (which it does) and reconnect (which it does NOT). So I tried

sudo ifdown eth0 and gotifconfig tells meso I am at a loss. How do I stop and restart the network interface short of rebooting the machine?

TIA,

Ken

You can't do both at the same time.
Did you apply and close the network manager after unchecking the Enable Networking box ?

For the 'buntus:

sudo /etc/init.d/networking restart

And it'll apply the conditions you have specified in your /etc/network/interfaces file, which is generally more reliable than using "Network Manager".

If you prefer the GUI, wicd is a very good replacement for NM, and I recommend it. You'll need to add the wicd repository to /etc/apt/sources.lst before you can install it.

deb http://apt.wicd.net [ grumpy | hardy | karmic ] extras

Actually I did not open the network manager - at least when testing. I right click on the network icon uncheck "Enable Networking". The list goes away. I then right click again and check "Enable Networking". The network never comes back.

This works fine on the wireless connection on my netbook running Ubuntu 9.04. Just checked - it also works fine with a wired connection on the netbook.

I did notice that the wired connection is called "Auto eht0" on the netbook and ifdown --help states in part So let me post this and try -a and also see if I can figure out if my desktop eth0 is "auto"

Ken

OK, so it seems that ifdown and ifup are not the proper command. So I tried your suggestion tredegar. Here is what I have experienced.

I unchecked then rechecked Enable Networking then ran the buntu command. The network never came back until I rebooted.

I made a change to "Wired connection 1" with the Network Manager applet then ran the buntu command. The change was not recognized. I did see this on the first execution of the command after reboot. Subsequent times it does not complain about eth0(?)
And my /etc/network/interfaces file contains no eth0
So where is eth0 coming from? According to ifconfig it is the interface which I am using.

Ken

That first quote you give is some kind of clue.
"Ignoring unknown interface eth0=eth0."

Somewhere eth0 is defined as eth0=eth0

?

What is in /etc/udev/rules.d/70-persistent-net-rules?

By the way, network manager completely ignores /etc/network/interfaces - that file is used only if you configure networking manually.

But where is it defined (or not properly defined)? Interestingly the entry in the Network Connections dialog shows "Network Connection 1" - my wired connection - as Last Used "never". However, Network Connection 1 is where I have defined the static IP address of the machine and it does in fact get that IP address.

I am going out for a walk.

Ken

I know what you mean.

So I found a site which explains how to setup networking in Ubuntu. I added the following to /etc/network/interfaces
I can restart this using ifconfig will show me the IP address I assign. However, when I changed the IP address to something different than Network Manager had (for testing) it killed the connection pending a reboot.

Well - enough of this horse manure - I tested Network Manager on Lucid Lynx alpha 3 and it works as expected. I hope Canonical leaves it alone when they go into production.

Ken